The present invention relates to a catalyst heating control apparatus suitable for cleaning exhaust gases from automotive engines.
In conventional heating control devices, as discussed in the SAX, Technical Paper, Series, 900503 (1990) page 61-70, the catalyst is formed on a resister type metallic carrier, which is heated by passing a current through it. Such catalyst heating control devices are designed to heat the catalyst to about 350.degree. C. (the catalyst activation temperature) within 30 seconds by using a conventional 12-V power supply system. The control includes a catalyst heating current supply and a catalyst temperature sensor in order to heat the catalyst to a desired operation temperature. Such conventional catalyst control device can improve the exhaust gas quality at low temperatures.
The above-mentioned conventional art has no special power supply that supplies current to the catalyst. Neither is any provision made to curtail the flow of current to the catalyst during cranking of the engine by the starter motor when the engine is started. When the charging capacity of the battery drops due to use of the engine battery to heat the catalyst, it becomes difficult to start the engine. This is a significant problem because the power required to heat the catalyst is about 4.7 kW, which is a significant burden for the conventional power supply, and leads to possible discharges and degradation of the power unit.
Moreover, to minimize pollution of the atmosphere by exhaust gases, it is desirable to preheat the catalyst prior to the start of the engine so that the catalyst is at a temperature as close as possible to the catalyst activation temperature when the engine is started. Frequent heating of the catalyst, however, can result in degradation of the charging capability of the power supply, which in turn degrades the performance of the engine's starter motor, absent protective measures provided in the method and apparatus according to the invention.